Have you asked the company looking after the heat pump etc. for a recommendation? Our geothermal company sorted out the driller for us, if you have not already picked a geothermal company I would happily recommend the guys we used ([broken link removed], a Clonakilty based Company) as we ran into problems and have had masses of testing done to ensure the project is viable and the system will be efficient. I have no connection with them, just a happy customer!!